Myeloperoxidase is critically involved in the induction of organ damage after renal ischemia reperfusion

Dexmedetomidine alleviates acute kidney injury in a rat model of veno-arterial extracorporeal membrane oxygenation

BACKGROUND

Although extracorporeal membrane oxygenation (ECMO) is an effective technique for life support, the incidence of acute kidney injury (AKI) during ECMO support remains high. Dexmedetomidine (DEX), which has been widely used for sedation during ECMO, possesses several properties that help reduce the occurrence of AKI. This study aimed to investigate the protective effect of DEX on kidney function during ECMO.

METHODS

A total of 18 male Sprague-Dawley (SD) rats were randomly divided into three groups: Sham, ECMO, and ECMO + DEX groups. ECMO was established through the right jugular vein for venous drainage and right femoral artery for arterial infusion and lasts for four hours. Hematoxylin and eosin staining was used to evaluate the kidney Paller score for the rats in each group. Enzyme-linked immunosorbent assay was used to measure the levels of kidney injury biomarkers and cytokines in the serum. Reagent kits were used to measure the blood urea nitrogen (BUN) and creatinine (Cr) levels, which helped determine kidney function. Immunohistochemical staining was used to evaluate neutrophil infiltration in the kidney.

RESULTS

The pathological Paller score was substantially lower in the ECMO + DEX group. The levels of Kidney Injury Molecule-1 (KIM-1) and N-acetyl-β-D-glucosaminidase (NAG) were also significantly reduced. The kidney functionality, as indicated by BUN and Cr, was significantly improved compared with the ECMO group. The levels of cytokines IL-6, IL-1β, and TNF-α, were also significantly decreased in the ECMO + DEX group.

CONCLUSION

This study demonstrated that dexmedetomidine could reduce inflammatory response and alleviate AKI during ECMO support.

Normothermic ex vivo kidney perfusion preserves mitochondrial and graft function after warm ischemia and is further enhanced by AP39

We previously reported that normothermic ex vivo kidney  perfusion (NEVKP) is superior in terms of organ protection compared to static cold storage (SCS), which is still the standard method of organ preservation, but the mechanisms are incompletely understood. We used a large animal kidney autotransplant model to evaluate mitochondrial function during organ preservation and after kidney transplantation, utilizing live cells extracted from fresh kidney tissue. Male porcine kidneys stored under normothermic perfusion showed preserved mitochondrial function and higher ATP levels compared to kidneys stored at 4 °C (SCS). Mitochondrial respiration and ATP levels were further enhanced when AP39, a mitochondria-targeted hydrogen sulfide donor, was administered during warm perfusion. Correspondingly, the combination of NEVKP and AP39 was associated with decreased oxidative stress and inflammation, and with improved graft function after transplantation. In conclusion, our findings suggest that the organ-protective effects of normothermic perfusion are mediated by maintenance of mitochondrial function and enhanced by AP39 administration. Activation of mitochondrial function through the combination of AP39 and normothermic perfusion could represent a new therapeutic strategy for long-term renal preservation.

Propionyl-l-carnitine mitigates ischemia-reperfusion injury in rat epigastric island flaps

BACKGROUND

Ischemia-reperfusion injury presents a substantial concern in various medical scenarios, notably in reconstructive surgery involving tissue flaps. Despite reports on the protective benefits of Propionyl-l-carnitine against ischemia-reperfusion injury, a thorough assessment of its efficacy in epigastric island flap models is currently lacking.

METHODS

Sixteen male Sprague-Dawley rats underwent epigastric island flap surgery and were divided into two groups: a Propionyl-l-carnitine group that received intraperitoneal Propionyl-l-carnitine prior to ischemia induction and a sham group that received saline treatment. A comprehensive evaluation was performed including macroscopic, biochemical and histological assessments encompassing measurements of flap survival areas, lipid peroxidation (malondialdehyde), glutathione, myeloperoxidase, nitric oxide and peripheral neutrophil counts.

RESULTS

The Propionyl-l-carnitine group demonstrated significantly increased flap survival areas when compared to the sham group. Administration of Propionyl-l-carnitine led to reduced malondialdehyde levels and elevated glutathione levels indicating a reduction in oxidative stress. Furthermore, the Propionyl-l-carnitine group exhibited lower myeloperoxidase levels, higher nitric oxide levels and reduced peripheral neutrophil counts, suggesting a decrease in the inflammatory response. Histopathological analysis revealed decreased levels of inflammation, necrosis, polymorphonuclear leukocyte infiltration and edema in the Propionyl-l-carnitine group. Additionally, vascularity was enhanced in the Propionyl-l-carnitine group.

CONCLUSION

This study provides compelling evidence that Propionyl-l-carnitine administration effectively mitigates the deleterious effects of ischemia-reperfusion injury in epigastric island flaps. This is substantiated by the improved flap survival, diminished oxidative stress and inflammation, as well as the enhanced vascularity observed. Propionyl-l-carnitine emerges as a promising therapeutic intervention to enhance tissue flap survival in reconstructive surgery, warranting further exploration through larger-scale investigations.

Metformin alleviates lung ischemia-reperfusion injury in a rat lung transplantation model

Background: Lung ischemia-reperfusion injury (LIRI) is among the complications observed after lung transplantation and is associated with morbidity and mortality. Preconditioning of the donor lung before organ retrieval may improve organ quality after transplantation. We investigated whether preconditioning with metformin (Met) ameliorates LIRI after lung transplantation. Methods: Twenty Lewis rats were randomly divided into the sham, LIRI, and Met groups. The rats in the LIRI and Met groups received saline and Met, respectively, via oral gavage. Subsequently, a donor lung was harvested and kept in cold storage for 8 h. The LIRI and Met groups then underwent left lung transplantation. After 2 h of reperfusion, serum and transplanted lung tissues were examined. Results: The partial pressure of oxygen (PaO2) was greater in the Met group than in the LIRI group. In the Met group, wet-to-dry (W/D) weight ratios, inflammatory factor levels, oxidative stress levels and apoptosis levels were notably decreased. Conclusions: Met protects against ischemia-reperfusion injury after lung transplantation in rats, and its therapeutic effect is associated with its anti-inflammatory, antioxidative, and antiapoptotic properties.

Reduction of neutrophil extracellular traps accelerates inflammatory resolution and increases bone formation on titanium implants

Neutrophils are the most abundant immune cells in the blood and the first cells to be recruited to the biomaterial implantation site. Neutrophils are fundamental in recruiting mononuclear leukocytes to mount an immune response at the injury site. Neutrophils exert significant pro-inflammatory effects through the release of cytokines and chemokines, degranulation and release of myeloperoxidase (MPO) and neutrophil elastase (NE), and the production of large DNA-based networks called neutrophil extracellular traps (NETs). Neutrophils are initially recruited and activated by cytokines and pathogen- and damage-associated molecular patterns, but little is known about how the physicochemical composition of the biomaterial affects their activation. This study aimed to understand how ablating neutrophil mediators (MPO, NE, NETs) affected macrophage phenotype in vitro and osseointegration in vivo. We discovered that NET formation is a crucial mediator of pro-inflammatory macrophage activation, and inhibition of NET formation significantly suppresses macrophage pro-inflammatory phenotype. Furthermore, reducing NET formation accelerated the inflammatory phase of healing and produced greater bone formation around the implanted biomaterial, suggesting that NETs are essential regulators of biomaterial integration. Our findings emphasize the importance of the neutrophil response to implanted biomaterials and highlight innate immune cells' regulation and amplification signaling during the initiation and resolution of the inflammatory phase of biomaterial integration. STATEMENT OF SIGNIFICANCE: Neutrophils are the most abundant immune cells in blood and are the first to be recruited to the injury/implantation site where they exert significant pro-inflammatory effects. This study aimed to understand how ablating neutrophil mediators affected macrophage phenotype in vitro and bone apposition in vivo. We found that NET formation is a crucial mediator of pro-inflammatory macrophage activation. Reducing NET formation accelerated the inflammatory phase of healing and produced greater appositional bone formation around the implanted biomaterial, suggesting that NETs are essential regulators of biomaterial integration.

Myeloperoxidase: Regulation of Neutrophil Function and Target for Therapy

Neutrophils, the most abundant white blood cells in humans, are critical for host defense against invading pathogens. Equipped with an array of antimicrobial molecules, neutrophils can eradicate bacteria and clear debris. Among the microbicide proteins is the heme protein myeloperoxidase (MPO), stored in the azurophilic granules, and catalyzes the formation of the chlorinating oxidant HOCl and other oxidants (HOSCN and HOBr). MPO is generally associated with killing trapped bacteria and inflicting collateral tissue damage to the host. However, the characterization of non-enzymatic functions of MPO suggests additional roles for this protein. Indeed, evolving evidence indicates that MPO can directly modulate the function and fate of neutrophils, thereby shaping immunity. These actions include MPO orchestration of neutrophil trafficking, activation, phagocytosis, lifespan, formation of extracellular traps, and MPO-triggered autoimmunity. This review scrutinizes the multifaceted roles of MPO in immunity, focusing on neutrophil-mediated host defense, tissue damage, repair, and autoimmunity. We also discuss novel therapeutic approaches to target MPO activity, expression, or MPO signaling for the treatment of inflammatory and autoimmune diseases.

Beneficial Effects of Insulin on Ischemia Reperfusion Injury in Human Skeletal Muscle

Purpose

Exaggerated leucocyte activity is a crucial step in the pathophysiology of skeletal muscle ischemia-reperfusion injury (IRI). We tested the hypothesis that insulin, via its' anti-leukocyte activity, attenuates skeletal muscle IRI in humans.

Materials and Methods

This randomized, blinded, placebo-controlled trial was conducted in patients with skeletal muscle ischemia who required revascularization. Treatment protocols were similar among them except for the insulin group, which received an infusion of insulin at 2.5 U/h. The degree of endothelial adhesiveness; leukocyte activity and pro-inflammatory status via P-selectin, tumor necrosis factor (TNF)-alpha, and myeloperoxidase (MPO) levels in the venous effluent; and clinical outcomes were measured.

Results

Twenty-four consenting patients were randomized to the insulin or control group. There were no significant differences between the two groups except for the median serum insulin level, which was higher in the insulin group (P<0.01). No serious intervention-related adverse events were observed. P-selectin (55.04-99.86 pg/mL; P<0.001), MPO (110.8-160.6 pg/mL; P<0.001), and TNF-alpha (12.16-36.01 pg/mL; P<0.001) levels demonstrated a significant increase post-reperfusion in the 'control' group, reaching a peak value at 2 hours post-reperfusion. The increase in all three markers from baseline was significantly diminished in the insulin group at the two-hour (P-selectin, P=0.001; MPO, P=0.001; TNF-alpha, P=0.005) and four-hour (P-selectin, P=0.003; MPO, P=0.002; TNF-alpha, P=0.01) intervals. The differences in clinical outcomes between the insulin and control groups were not statistically significant.

Conclusion

In clinical practice, insulin has the potential to attenuate the severity of skeletal muscle IRI inhibiting P-selectin, MPO, and TNF-alpha levels.

Renoprotective effect of vinpocetine against ischemia/reperfusion injury: Modulation of NADPH oxidase/Nrf2, IKKβ/NF-κB p65, and cleaved caspase-3 expressions

Ischemia/reperfusion injury (IRI) during kidney transplantation is a serious clinical problem with a high mortality rate and a lack of therapy. Therefore, there is a need to improve the ability of the kidney to tolerate IRI during transplantation. This study aimed to investigate the possible protective effect of vinpocetine; a derivative of vincamine alkaloid; against renal IRI in rats with the elucidation of the involved mechanisms. Vinpocetine (25 mg/kg; i.p.) was administered for 10 successive days before the induction of ischemia by bilateral clamping of both renal pedicles for 45 min followed by 24 h of reperfusion. Blood and renal tissue samples were then collected for biochemical, molecular, and histopathological investigations. Vinpocetine significantly reduced serum creatinine and blood urea nitrogen levels in rats subjected to IRI. It also reduced mRNA expression of NADPH oxidase and renal content of malondialdehyde, while enhanced Nrf2 protein expression and renal content of reduced glutathione. The suppression of the provoked inflammatory response was evident by the downregulation of IKKβ and NF-κB p65 protein expressions, as well as their downstream inflammatory markers; tumor necrosis factor-α, interleukin-6, and myeloperoxidase. In addition, vinpocetine reduced protein expression of the apoptotic executioner cleaved caspase-3. These nephroprotective effects were confirmed by the improvement in histopathological features. Collectively, the protective effect of vinpocetine against IRI could be attributed to modulation of NADPH oxidase/Nrf2, IKKβ/NF-κB p65, and cleaved caspase-3 expressions. Thus, vinpocetine could improve oxidant/antioxidant balance, suppress triggered inflammatory response, and promote renal cell survival after IRI.

Targeting Neutrophils for Promoting the Resolution of Inflammation

Acute inflammation is a localized and self-limited innate host-defense mechanism against invading pathogens and tissue injury. Neutrophils, the most abundant immune cells in humans, play pivotal roles in host defense by eradicating invading pathogens and debris. Ideally, elimination of the offending insult prompts repair and return to homeostasis. However, the neutrophils` powerful weaponry to combat microbes can also cause tissue damage and neutrophil-driven inflammation is a unifying mechanism for many diseases. For timely resolution of inflammation, in addition to stopping neutrophil recruitment, emigrated neutrophils need to be disarmed and removed from the affected site. Accumulating evidence documents the phenotypic and functional versatility of neutrophils far beyond their antimicrobial functions. Hence, understanding the receptors that integrate opposing cues and checkpoints that determine the fate of neutrophils in inflamed tissues provides insight into the mechanisms that distinguish protective and dysregulated, excessive inflammation and govern resolution. This review aims to provide a brief overview and update with key points from recent advances on neutrophil heterogeneity, functional versatility and signaling, and discusses challenges and emerging therapeutic approaches that target neutrophils to enhance the resolution of inflammation.

Lipoxin A4 attenuates the lung ischaemia reperfusion injury in rats after lung transplantation

BACKGROUND

Lung ischaemia reperfusion injury (LIRI) is the major cause of primary lung dysfunction after lung transplantation. Lipoxin A4 inhibits the oxidative stress and inflammation. This study aimed to evaluate the potential protective effect of lipoxin A4 on LIRI in rats.

METHODS

SD (Sprague-Dawley) rats were randomised into the sham, LIRI and LA4 groups. Rats in the sham group received anaesthesia, thoracotomy and intravenous injection of saline, while those in the LIRI or LA4 group received left lung transplantation and intravenous injection of saline or lipoxin A4, respectively. After 24 h of reperfusion, the PaO₂/FiO₂ (Partial pressure of O2 to fraction inspiratory O2), wet/dry weight ratios and protein levels in lungs were measured to assess the alveolar capillary permeability. The oxidative stress response and inflammation were examined. The histological and apoptosis analyses of lung tissues were performed via HE staining (Haematoxylin-eosin staining) and TUNEL assay, respectively. The effects of lipoxin A4 on the endothelial viability and tube formation of hypoxaemia and reoxygenation-challenged rat pulmonary microvascular endothelium cells were determined.

RESULTS

Lipoxin A4 significantly ameliorated the alveolar capillary permeability, reduced the oxidative stress and inflammation in transplanted lungs. The histological injury and apoptosis of lung tissues were also alleviated by lipoxin A4. In vitro lipoxin A4 treatment promoted the endothelial tube formation and improved the endothelial viability.

CONCLUSION

Lipoxin A4 protects LIRI after lung transplantation in rats, and its therapeutic effect is associated with the properties of anti-inflammation, anti-oxidation, and endothelium protection.Key messages:Lung transplantation is a treatment approach for the patients with lung disease.LIRI is the major cause of postoperative primary lung dysfunction.Lipoxins A4 exhibits strong anti-inflammatory properties.

Custodiol® Supplemented with Synthetic Human Relaxin Decreases Ischemia-Reperfusion Injury after Porcine Kidney Transplantation

Objective. Ischemia-reperfusion injury (IRI) is inevitable after kidney transplantation (KT), impairing outcomes. Relaxin-2 (RLX) is a promising insulin-related peptide hormone that protects against renal IRI in rodents, although large animal models are needed before RLX can be tested in a human setting. Methods. In this blinded, randomized, and placebo-controlled experimental study kidneys from 19 donor pigs were retrieved after perfusion with Custodiol® ± RLX (5 or 20 nmol/L) and underwent static cold storage (SCS) for 24 and 48 h, respectively. Subsequently, KT was performed after unilateral right nephrectomy. Study outcomes included markers for kidney function, oxidative stress, lipid peroxidation, and endothelial cell damage. PCR analysis for oxidative stress and apoptosis-related gene panels as well as immunohistochemistry were performed. Results. RLX upregulated SOD2 and NFKB expression to 135% (p = 0.042) and 125% (p = 0.019), respectively, while RIPK1 expression was downregulated to 82% (p = 0.016) of corresponding controls. Further RLX significantly downregulated RIPK1 and MLKL expression and decreased the number of Caspase 3- and MPO-positive cells in grafts after SCS. Conclusions. RLX supplemented Custodiol® significantly decreased IRI via both antioxidant and anti-apoptotic mechanisms. Clinical trials are warranted to implement synthetic human RLX as a novel additive to preservation solutions against IRI.

Roles of neutrophil granule proteins in orchestrating inflammation and immunity

Neutrophil granulocytes form the first line of host defense against invading pathogens and tissue injury. They are rapidly recruited from the blood to the affected sites, where they deploy an impressive arsenal of effectors to eliminate invading microbes and damaged cells. This capacity is endowed in part by readily mobilizable proteins acquired during granulopoiesis and stored in multiple types of cytosolic granules with each granule type containing a unique cargo. Once released, granule proteins contribute to killing bacteria within the phagosome or the extracellular milieu, but are also capable of inflicting collateral tissue damage. Neutrophil-driven inflammation underlies many common diseases. Research over the last decade has documented neutrophil heterogeneity and functional versatility far beyond their antimicrobial function. Emerging evidence indicates that neutrophils utilize granule proteins to interact with innate and adaptive immune cells and orchestrate the inflammatory response. Granule proteins have been identified as important modulators of neutrophil trafficking, reverse transendothelial migration, phagocytosis, neutrophil life span, neutrophil extracellular trap formation, efferocytosis, cytokine activity, and autoimmunity. Hence, defining their roles within the inflammatory locus is critical for minimizing damage to the neighboring tissue and return to homeostasis. Here, we provide an overview of recent advances in the regulation of degranulation, granule protein functions, and signaling in modulating neutrophil-mediated immunity. We also discuss how targeting granule proteins and/or signaling could be harnessed for therapeutic benefits.

Myeloperoxidase: A versatile mediator of endothelial dysfunction and therapeutic target during cardiovascular disease

Myeloperoxidase (MPO) is a prominent mammalian heme peroxidase and a fundamental component of the innate immune response against microbial pathogens. In recent times, MPO has received considerable attention as a key oxidative enzyme capable of impairing the bioactivity of nitric oxide (NO) and promoting endothelial dysfunction; a clinically relevant event that manifests throughout the development of inflammatory cardiovascular disease. Increasing evidence indicates that during cardiovascular disease, MPO is released intravascularly by activated leukocytes resulting in its transport and sequestration within the vascular endothelium. At this site, MPO catalyzes various oxidative reactions that are capable of promoting vascular inflammation and impairing NO bioactivity and endothelial function. In particular, MPO catalyzes the production of the potent oxidant hypochlorous acid (HOCl) and the catalytic consumption of NO via the enzyme's NO oxidase activity. An emerging paradigm is the ability of MPO to also influence endothelial function via non-catalytic, cytokine-like activities. In this review article we discuss the implications of our increasing knowledge of the versatility of MPO's actions as a mediator of cardiovascular disease and endothelial dysfunction for the development of new pharmacological agents capable of effectively combating MPO's pathogenic activities. More specifically, we will (i) discuss the various transport mechanisms by which MPO accumulates into the endothelium of inflamed or diseased arteries, (ii) detail the clinical and basic scientific evidence identifying MPO as a significant cause of endothelial dysfunction and cardiovascular disease, (iii) provide an up-to-date coverage on the different oxidative mechanisms by which MPO can impair endothelial function during cardiovascular disease including an evaluation of the contributions of MPO-catalyzed HOCl production and NO oxidation, and (iv) outline the novel non-enzymatic mechanisms of MPO and their potential contribution to endothelial dysfunction. Finally, we deliver a detailed appraisal of the different pharmacological strategies available for targeting the catalytic and non-catalytic modes-of-action of MPO in order to protect against endothelial dysfunction in cardiovascular disease.

Eicosanoid production varies by sex in mesenteric ischemia reperfusion injury

Intestinal ischemia/reperfusion (I/R)-induced injury is an inflammatory response with significant morbidity and mortality. The early inflammatory response includes neutrophil infiltration. However, the majority of rodent studies utilize male mice despite a sexual dimorphism in intestinal I/R-related diseases. We hypothesized that sex may alter inflammation by changing neutrophil infiltration and eicosanoid production. To test this hypothesis, male and female C57Bl/6 mice were subjected to sham treatment or 30 min intestinal ischemia followed by a time course of reperfusion. We demonstrate that compared to male mice, females sustain significantly less intestinal I/R-induced tissue damage and produced significant LTB₄ concentrations. Male mice release PGE₂. Finally, treatment with a COX-2 specific inhibitor, NS-398, attenuated I/R-induced injury, total peroxidase level, and PGE₂ production in males, but not in similarly treated female mice. Thus, I/R-induced eicosanoid production and neutrophil infiltration varies between sexes suggesting that distinct therapeutic intervention may be needed in clinical ischemic diseases.

Neutrophil heterogeneity and fate in inflamed tissues: implications for the resolution of inflammation

Neutrophils are polymorphonuclear leukocytes that play a central role in host defense against infection and tissue injury. They are rapidly recruited to the inflamed site and execute a variety of functions to clear invading pathogens and damaged cells. However, many of their defense mechanisms are capable of inflicting collateral tissue damage. Neutrophil-driven inflammation is a unifying mechanism underlying many common diseases. Efficient removal of neutrophils from inflammatory loci is critical for timely resolution of inflammation and return to homeostasis. Accumulating evidence challenges the classical view that neutrophils represent a homogeneous population and that halting neutrophil influx is sufficient to explain their rapid decline within inflamed loci during the resolution of protective inflammation. Hence, understanding the mechanisms that govern neutrophil functions and their removal from the inflammatory locus is critical for minimizing damage to the surrounding tissue and for return to homeostasis. In this review, we briefly address recent advances in characterizing neutrophil phenotypic and functional heterogeneity and the molecular mechanisms that determine the fate of neutrophils within inflammatory loci and the outcome of the inflammatory response. We also discuss how these mechanisms may be harnessed as potential therapeutic targets to facilitate resolution of inflammation.

Terminalia catappa L. infusion accelerates the healing process of gastric ischemia-reperfusion injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Terminalia catappa L. (Combretaceae), known as "amendoeira da praia" in Brazil, has been recognized as a medicinal plant in folk medicine for the treatment of gastrointestinal disorders and other inflammatory conditions. The present study aimed to investigate the preventive and healing effects of the infusion of leaves of T. catappa (ILTC) against gastric lesions caused by ischemia and reperfusion (I/R) injury and characterize its mechanism of action in the gastric mucosa of rats.

MATERIALS AND METHODS

Different doses (30, 100, and 300 mg/kg) of ILTC were orally administered as acute and subacute treatments against I/R-induced gastric lesion in rats. After treatment, the stomach of rats was collected to measure the lesion area, redox parameters malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and reduced glutathione (GSH) and inflammatory parameters myeloperoxidase activity (MPO), interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α). The activities of matrix metalloproteinases 2 and 9 (MMPs 2 and 9) were assessed by zymography method to clarify the mechanisms of the healing acceleration promoted by ILTC.

RESULTS

Pretreatment with ILTC (100 mg/kg) was effective in preventing the aggravation of lesions in the acute model by reducing MPO activity by 38% relative to control group, despite the lack of clarity of this action at the macroscopical level at the lesion area (p < 0.05). After three days of treatment with ILTC (30 and 100 mg/kg), this infusion significantly reduced the lesion area by 95% and 89%, respectively, compared the control (p < 0.05). The gastric healing effect of all doses of ILTC was followed by a reduction in MPO activity (decrease by 70-78%). Compared to the negative control, an improvement in gastric healing owing to treatment with ILTC was observed and this was followed by an increase in MMP-2 (20-47%) (p < 0.05).

CONCLUSION

Three days of treatment with ILTC could accelerate the healing process in I/R-induced lesions in rats. By decreasing MPO levels, ILTC enabled the action of MMP-2, which led to tissue recovery in the gastric mucosa.

A two-stage bilateral ischemia-reperfusion injury-induced AKI to CKD transition model in mice

Acute kidney injury (AKI) significantly increases the risk of development of chronic kidney disease (CKD). Recently, our laboratory generated a mouse model with the typical phenotypes of AKI to CKD transition in the unilateral kidney. However, AKI, CKD, and even the transition from AKI to CKD usually occur bilaterally rather than unilaterally in patients. Therefore, in the present study, we further modified the strategy and developed a new model of CKD transitioned from bilateral ischemia-reperfusion injury (IRI) in C57BL/6 mice. In this new model, unilateral severe IRI was performed in one kidney while the contralateral kidney was kept intact to maintain animal survival; then, following 14 days of recovery, when the renal function of the injured kidney restored above the survival threshold, the contralateral intact kidney was subjected to a similar IRI. Animals of these two-stage bilateral IRI models with pedicle clamping of 21 and 24 min at a body temperature of 37°C exhibited incomplete recovery from AKI and subsequent development of CKD with characteristics of progressive decline in glomerular filtration rate, increases in plasma creatinine, worsening of proteinuria, and deleterious histopathological changes, including interstitial fibrosis and glomerulosclerosis, in both kidneys. In conclusion, a new bilateral AKI to CKD transition animal model with a typical phenotype of CKD was generated in C57BL/6 mice.

Immune response and Raman scattering assessment in rats skin after contact with Fusarium oxysporum metabolites

The secondary metabolites produced by Fusarium can cause disease and death when consumed and produce biological responses even in the absence of the microorganism. The IL-6, TNF-α and TGF-β1 cytokines immune reactivity was associated with histopathological and physico-chemical changes in skin of immune competent rats after administration of Fusarium oxysporum crude extract. Rats were intradermally injected with 50 μl of 0.5 mg/ml crude extract and were euthanized at 3, 6, 12 and 24 h after injection. The inflammatory response was quantified by enzyme myeloperoxidase activity and by immunohistochemical method to detect the IL-6, TNF-α and TGF-β1. Physico-chemical analysis was performed using FT-Raman Spectroscopy. The inflammatory response was most intense at 6 and 12 h after crude extract administration and the most significant histopathological changes were observed in the dermis. Myeloperoxidase activity was intense from 3 to 24 h after injection. The immunostaining of pro-inflammatory cytokines IL-6 and TNF-α peaked at 6 h. Immunostaining for TGF-β1 was highest at 12 and 24 h. FT-Raman spectral analysis showed both, the most intense Fusarium interaction with the skin at 6 h, as revealed by the changes in the stretching of -CH bands (3100-2800 cm^-1) in the dermis, and skin recovery trending after 12 h after crude extract injection. The results showed that secondary metabolites stimulated histopathologic changes and inflammatory responses even in the absence of the fungus, increasing myeloperoxidase activity and pro-inflammatory cytokine expression besides promoting physico-chemical changes.

Thioredoxin-2 impacts the inflammatory response via suppression of NF-κB and MAPK signaling in sepsis shock

Sepsis is a progressive disease characterized by excessive inflammatory responses, severe tissue injury and organ dysfunction, ultimately leading to mortality. In this study, we demonstrated that thioredoxin-2 (TRX-2) expression is reduced in macrophages stimulated with lipopolysaccharide (LPS). Overexpression of TRX-2 significantly attenuated interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) production induced by LPS. TRX-2 inhibited LPS-induced inflammatory responses through suppressing activation of the NF-κB and MAPK signaling pathways. Furthermore, TRX-2 induced a significant decrease in mortality in mouse sepsis models in association with reduced inflammatory cytokine production and attenuation of organ injury. Our data collectively support a role of TRX-2 as a critical regulator of sepsis that influences survival by protecting the host from excessive inflammatory damage.

Exosomes from mesenchymal stromal cells reduce murine colonic inflammation via a macrophage-dependent mechanism

Conventional treatments for inflammatory bowel disease (IBD) have multiple potential side effects. Therefore, alternative treatments are desperately needed. This work demonstrated that systemic administration of exosomes from human bone marrow-derived mesenchymal stromal cells (MSC-Exos) substantially mitigated colitis in various models of IBD. MSC-Exos treatment downregulated inflammatory responses, maintained intestinal barrier integrity, and polarized M2b macrophages but did not favor intestinal fibrosis. Mechanistically, infused MSC-Exos acted mainly on colonic macrophages, and macrophages from colitic colons acquired obvious resistance to inflammatory restimulation when prepared from mice treated with MSC-Exos versus untreated mice. The beneficial effect of MSC-Exos was blocked by macrophage depletion. Also, the induction of IL-10 production from macrophages was partially involved in the beneficial effect of MSC-Exos. MSC-Exos were enriched in proteins involved in regulating multiple biological processes associated with the anticolitic benefit of MSC-Exos. Particularly, metallothionein-2 in MSC-Exos was required for the suppression of inflammatory responses. Taken together, MSC-Exos are critical regulators of inflammatory responses and may be promising candidates for IBD treatment.

Myeloperoxidase-mediated oxidation of edaravone produces an apparent non-toxic free radical metabolite and modulates hydrogen peroxide-mediated cytotoxicity in HL-60 cells

Edaravone is considered to be a potent antioxidant drug known to scavenge free radical species and prevent free radical-induced lipid peroxidation. In this study, we investigated the effect of edaravone on the myeloperoxidase (MPO) activity, an enzyme responsible for the production of an array of neutrophil-derived oxidants that can cause cellular damage. The addition of edaravone to the reaction of MPO and hydrogen peroxide (H₂O₂) significantly enhanced the reduction of MPO Compound II back to native MPO. Interestingly, the MPO-mediated production of toxic hypochlorous acid exhibited a concentration-dependent biphasic effect, with the apparent optimal edaravone concentration at 10 μM. Oxidation of edaravone by MPO was examined by various analytical methods. An MPO-catalyzed product(s) of edaravone was identified at 350 nm by kinetic analysis of UV-Vis spectroscopy. Several MPO-catalyzed metabolites of edaravone were proposed from the LC-MS analyses, including oxidized dimers from edaravone radicals. Electron spin resonance (ESR) spin trapping detected a carbon-centred radical metabolite of edaravone. NMR studies revealed that there are two exchangeable hydrogens, one of which is on the α-carbon, justifying the carbon-centred edaravone radical produced from MPO. Despite the formation of an edaravone carbon-radical metabolite, it did not appear to effectively oxidize GSH (in comparison with phenoxyl radicals). Viability (ATP) and cytotoxicity (LDH release) assays showed a concentration-dependent effect of edaravone on HL-60 cells treated with either a bolus concentration of 30 μM H₂O₂ or a flux of H₂O₂ generated by 5 mM glucose and 10 mU/mL glucose oxidase. The H₂O₂-induced toxicity was ameliorated at high edaravone concentrations (100-200 μM). In contrast, low concentrations of edaravone (1-10 μM) exacerbated the H₂O₂-induced toxicity. However, the effect of edaravone at low concentration (0-10 μM) appeared more prominent with the LDH assay only. The cellular findings correlated with the biochemical studies with respect to hypochlorous acid formation. These findings provide interesting perspectives regarding the duality of edaravone as an antioxidant drug.

Mast cell chymase protects against acute ischemic kidney injury by limiting neutrophil hyperactivation and recruitment

Here we investigated the role of murine mast cell protease 4 (MCPT4), the functional counterpart of human mast cell chymase, in an experimental model of renal ischemia reperfusion injury, a major cause of acute kidney injury. MCPT4-deficient mice had worsened kidney function compared to wildtype mice. MCPT4 absence exacerbated pathologic neutrophil infiltration in the kidney and increased kidney myeloperoxidase expression, cell death and necrosis. In kidneys with ischemia reperfusion injury, when compared to wildtype mice, MCPT4-deficient mice showed increased surface expression of adhesion molecules necessary for leukocyte extravasation including neutrophil CD162 and endothelial cell CD54. In vitro, human chymase mediated the cleavage of neutrophil expressed CD162 and also CD54, P- and E-Selectin expressed on human glomerular endothelial cells. MCPT4 also dampened systemic neutrophil activation after renal ischemia reperfusion injury as neutrophils expressed more CD11b integrin and produced more reactive oxygen species in MCPT4-deficient mice. Accordingly, after renal injury, neutrophil migration to an inflammatory site distal from the kidney was increased in MCPT4-deficient versus wildtype mice. Thus, contrary to the described overall aggravating role of mast cells, one granule-released mediator, the MCPT4 chymase, exhibits a potent anti-inflammatory function in renal ischemia reperfusion injury by controlling neutrophil extravasation and activation thereby limiting associated damage.

Iodide modulates protein damage induced by the inflammation-associated heme enzyme myeloperoxidase

Iodide ions (I^-) are an essential dietary mineral, and crucial for mental and physical development, fertility and thyroid function. I^- is also a high affinity substrate for the heme enzyme myeloperoxidase (MPO), which is involved in bacterial cell killing during the immune response, and also host tissue damage during inflammation. In the presence of H₂O₂ and Cl^-, MPO generates the powerful oxidant hypochlorous acid (HOCl), with excessive formation of this species linked to multiple inflammatory diseases. In this study, we have examined the hypothesis that elevated levels of I^- would decrease HOCl formation and thereby protein damage induced by a MPO/Cl^-/H₂O₂ system, by acting as a competitive substrate. The presence of increasing I^- concentrations (0.1-10 μM; i.e. within the range readily achievable by oral supplementation in humans), decreased damage to both model proteins and extracellular matrix components as assessed by gross structural changes (SDS-PAGE), antibody recognition of parent and modified protein epitopes (ELISA), and quantification of both parent amino acid loss (UPLC) and formation of the HOCl-biomarker 3-chlorotyrosine (LC-MS) (reduced by ca. 50% at 10 μM I^-). Elevated levels of I^- ( > 1 μM) also protected against functional changes as assessed by a decreased loss of adhesion (eg. 40% vs. < 22% with >1 μM I^-) of primary human coronary artery endothelial cells (HCAECs), to MPO-modified human plasma fibronectin. These data indicate that low micromolar concentrations of I^-, which can be readily achieved in humans and are readily tolerated, may afford protection against cell and tissue damage induced by MPO.

Plasma Biomarkers as Potential Predictors of Functional Dependence in Daily Life Activities after Ischemic Stroke: A Single Center Study

Objective:

Despite advances made in the treatment of ischemic stroke, it still remains one of the leading causes of mortality and disability worldwide. The main objective of this study was to identify from a panel of 10 inflammatory markers and chemokines those biomarkers that have a potential predictive role in the evolution of disability and functional dependence in daily activities after an ischemic stroke.

Methods:

The study included 116 patients with ischemic stroke and 40 healthy volunteers matched for gender and age. Stroke severity was assessed by the National Institute of Health Stroke Scale (NIHSS) on admission and during hospitalization and functional mobility in daily activities by Barthel index (BI). Multiplex panel with 10 biomarkers [brain-derived neurotrophic factor (BDNF), platelet-derived growth factor (PDGF)-AA, PDGF-AB/BB, neural cell adhesion molecule (NCAM), cathepsin D, soluble vascular cell adhesion molecule (sVCAM), soluble intercellular cell adhesion molecule (sICAM), myeloperoxidase (MPO), regulated on activation, normal T cell expressed and secreted (RANTES), plasminogen activator inhibitor (PAI)-1] was analyzed on days 1 and 5 after admission using the xMAP technology.

Results:

Plasma concentrations of RANTES and NCAM were significantly lower in patients with ischemic stroke compared with healthy controls, while MPO and sICAM were significantly higher in patients versus controls. Plasma concentrations of sICAM, sVCAM, and RANTES significantly decreased during the analyzed period. For the first-day measurement, the bivariate analysis revealed the association of NIHSS on admission with sVCAM, and on discharge negative association with PDGF-AA, PDGR-AB/BB, BDNF, and RANTES. Plasma levels of PDGF-AA, PDGF-AB/BB, BDNF, and RANTES were found to be significantly lower in patients with BI ≤ 80, on day 5 after disease onset. PDGF-AA, PDGF-AB/BB, and BDNF were univariate and multivariate predictors for functional dependence in daily life activity (BI ≤ 80), having a protective effect (odds ratio < 1).

Conclusion:

Plasma levels of BDNF, PDGF-AA, and PDGF-AB/BB are independent predictors for functional dependency in daily life activities and may be useful prognostic markers in the evaluation of ischemic stroke patients.

Sensitivity and Specificity of the Platelet-Lymphocyte Ratio and the Neutrophil-Lymphocyte Ratio in Diagnosing Acute Mesenteric Ischemia in Patients Operated on for the Diagnosis of Mesenteric Ischemia: A Retrospective Case-Control Study

Aim: The present study aims to determine whether various hematological parameters and ratios of patients could be used to diagnose AMI. Materials and Methods: The subjects of the study are the patients who were hospitalized with an acute mesenteric ischemia (AMI) pre-diagnosis and underwent surgery as a consequence. The patients who were determined to have the diagnosis of AMI intraoperatively are categorized in the AMI Group. The patients whose operations do not reveal AMI (negative exploration) are categorized in the Control Group. These two groups are compared in terms of hematological parameters and rates. Results: In the study, the PLR (p = 0.017), NLR (p = 0.33), PDW (0.023), RDW (p = 0.025) values are significantly higher in the AMI group compared to the control group while the LYMP (p = 0.023) count is significantly lower. Conclusions: For the patients admitted to the emergency clinics with suspected AMI, the increased PLR, NLR, PDW, and RDW values together with the reduced lymphocyte count can be used to support the diagnosis.

Antioxidants as Renoprotective Agents for Ischemia during Partial Nephrectomy

Small renal masses have been diagnosed increasingly in recent decades, allowing surgical treatment by partial nephrectomy. This treatment option is associated with better renal function preservation, in comparison with radical nephrectomy. However, for obtaining a bloodless field during surgery, occlusion of renal artery and veins is often required, which results in transitory ischemia. The renal ischemia-reperfusion injury is associated with increased reactive oxygen species production leading to renal tissue damage. Thus, the use of antioxidants has been advocated in the partial nephrectomy perioperative period. Several antioxidants were investigated in regard to renal ischemia-reperfusion injury. The present manuscript aims to present the literature on the most commonly studied antioxidants used during partial nephrectomy. The results of experimental and clinical studies using antioxidants during partial nephrectomy are reported. Further, alimentary sources of some antioxidants are presented, stimulating future studies focusing on perioperative antioxidant-rich diets.

A novel approach to identifying and quantifying neutrophil extracellular trap formation in septic dogs using immunofluorescence microscopy

Background

Canine neutrophils release neutrophil extracellular traps (NETs) in response to lipopolysaccharide but NETs from clinical septic dogs had not been identified. The primary aim is to describe the methodology of identifying and quantifying neutrophil extracellular traps (NETs) in cytology samples of septic foci in dogs with sepsis using immunofluorescence microscopy. Cytology samples including endotracheal tracheal wash (ETW), bronchoalveolar lavage (BAL), abdominal and pleural effusion collected from 5 dogs (3 septic, 2 non-septic) were fixed, permeabilized and stained for myeloperoxidase (MPO), citrullinated histone H3 (citH3) and cell-free DNA (cfDNA). Fluorescence microscopy was used to identify and quantify NETs in 10 random views at 40× magnification. NETs were identified based on co-localization of MPO, citH3 and cfDNA. NETs were quantified as a ratio (number of NETs: number of neutrophils). Neutrophils were identified based on cytoplasmic MPO, cellular diameter and nuclear morphology.

Results

NETs were identified and quantified in all cytology samples collected from septic dogs. A small number of NETs was documented in one dog with sterile chronic bronchitis. No NETs were found in sterile abdominal effusion collected from one dog with congestive heart failure.

Conclusions

Immunofluorescence microscopy could be a useful tool for the study of NETs in dogs with clinical sepsis.

Rodent models of AKI-CKD transition

Acute kidney injury (AKI) is a contributing factor in the development and progression of chronic kidney disease (CKD). Despite rapid progresses, the mechanism underlying AKI-CKD transition remains largely unclear. Animal models recapitulating this process are crucial to the research of the pathophysiology of AKI-CKD transition and the development of effective therapeutics. In this review, we present the commonly used rodent models of AKI-CKD transition, including bilateral ischemia-reperfusion injury (IRI), unilateral IRI, unilateral IRI with contralateral nephrectomy, multiple episodes of IRI, and repeated treatment of low-dose cisplatin, diphtheria toxin, aristolochic acid, or folic acid. The main merits and pitfalls of these models are also discussed. This review provides helpful information for establishing reliable and clinically relevant models for studying post-AKI development of chronic renal pathologies and the progression to CKD.

Myeloperoxidase Negatively Regulates Neutrophil-Endothelial Cell Interactions by Impairing αMβ2 Integrin Function in Sterile Inflammation

Interactions of neutrophils with endothelial cells (ECs) and platelets contribute to tissue damage and vascular occlusion under sterile inflammatory conditions. However, the molecular mechanisms regulating the cell–cell interactions remain poorly understood. Previous studies suggest that reactive oxygen species, such as hydrogen peroxide (H₂O₂), produced from NADPH oxidase 2 play a critical role in platelet–neutrophil interactions by regulating the function of neutrophil αMβ2 integrin during sterile inflammation. In this study, we further demonstrate a crucial role for myeloperoxidase (MPO) in regulating the adhesive function of neutrophils through αMβ2 integrin. Using real-time fluorescence intravital microscopy and in vitro assays, we showed that loss of MPO promoted neutrophil–EC interactions and neutrophil emigration but did not affect neutrophil–platelet interactions under inflammatory conditions. Using genetic and pharmacologic approaches, we found that following agonist stimulation, MPO knockout (KO) neutrophils exhibited a significant increase in extracellular H₂O₂ and surface level of αMβ2 integrin and that these effects were dependent on MPO activity. Our in vivo studies using an ischemia/reperfusion-induced hepatic inflammation model revealed that compared to wild-type mice, neutrophils from MPO KO mice—displayed a pro-migratory phenotype while ameliorating tissue damage. These results suggest that MPO plays a negative role in the adhesive and migratory function of neutrophils by impairing αMβ2 integrin function under sterile inflammatory conditions.

Myeloperoxidase: Its role for host defense, inflammation, and neutrophil function

Myeloperoxidase (MPO) is a heme-containing peroxidase expressed mainly in neutrophils and to a lesser degree in monocytes. In the presence of hydrogen peroxide and halides, MPO catalyzes the formation of reactive oxygen intermediates, including hypochlorous acid (HOCl). The MPO/HOCl system plays an important role in microbial killing by neutrophils. In addition, MPO has been demonstrated to be a local mediator of tissue damage and the resulting inflammation in various inflammatory diseases. These findings have implicated MPO as an important therapeutic target in the treatment of inflammatory conditions. In contrast to its injurious effects at sites of inflammation, recent studies using animal models of various inflammatory diseases have demonstrated that MPO deficiency results in the exaggeration of inflammatory response, and that it affects neutrophil functions including cytokine production. Given these diverse effects, a growing interest has emerged in the role of this well-studied enzyme in health and disease.

Increased Neutrophil Secretion Induced by NLRP3 Mutation Links the Inflammasome to Azurophilic Granule Exocytosis

Heterozygous mutations in the NLRP3 gene in patients with cryopyrin associated periodic syndrome (CAPS) lead to hyper-responsive inflammasome function. CAPS is a systemic auto-inflammatory syndrome characterized by the activation of the innate immune system induced by elevated pro-inflammatory cytokines, but the involvement of selective innate immune cells in this process is not fully understood. Neutrophil secretion and the toxic components of their granules are mediators of inflammation associated with several human diseases and inflammatory conditions. Here, using the Nlrp3^A350V inducible mouse model (MWS CreT) that recapitulates human patients with the A352V mutation in NLRP3 observed in the Muckle-Wells sub-phenotype of CAPS, we studied the relationship between hyper-activation of the inflammasome and neutrophil exocytosis. Using a flow cytometry approach, we show that Nlrp3^A350V (MWS) neutrophils express normal basal levels of CD11b at the plasma membrane and that the upregulation of CD11b from secretory vesicles in response to several plasma membrane or endocytic agonist including the bacterial-derived mimetic peptide formyl-Leu-Met-Phe (fMLF) and the unmethylated oligonucleotide CpG is normal in MWS neutrophils. Significant but modest CD11b upregulation in MWS neutrophils compared to wild type was only observed in response to GM-CSF and CpG. The same pattern was observed for the secretion of matrix metalloproteinase-9 (MMP-9) from gelatinase granules in that MMP-9 secretion in MWS neutrophils was not different from that observed in wild-type neutrophils except when stimulated with GM-CSF and CpG. In contrast, azurophilic granule secretion, whose cargoes constitute the most toxic secretory and pro-inflammatory factors of the neutrophil, was markedly dysregulated in MWS neutrophils under both basal and stimulated conditions. This could not be attributed to paracrine effects of secretory cytokines because IL-1β secretion by neutrophils was undetectable under these experimental conditions. The increased azurophilic granule exocytosis in MWS neutrophils was attenuated by treatment with the neutrophil exocytosis inhibitor Nexinhib20. In agreement with a possible neutrophil contribution to systemic inflammation in CAPS, the levels of neutrophil secretory proteins were significantly elevated in the plasma from Nlrp3^A350V mice. Altogether, our data indicates an azurophilic granule-selective dysregulation of neutrophil exocytosis in CAPS.

Carbon monoxide and hydrogen sulphide reduce reperfusion injury in abdominal compartment syndrome

BACKGROUND

Carbon monoxide (CO)- and hydrogen sulphide-releasing molecules (CORM-3 and GYY4137, respectively) have been shown to be potent antioxidant and antiinflammatory agents at the tissue and systemic level. We hypothesized that both CORM-3 and GYY4137 would reduce the significant organ dysfunction associated with abdominal compartment syndrome (ACS).

MATERIAL AND METHODS

Randomized trial was conducted where ACS was maintained for 2 hours in 27 rats using an abdominal plaster cast and intraperitoneal CO₂ insufflation at 20 mmHg. Three experimental groups underwent ACS and received an experimental molecule at the time of decompression: inactive CORM-3, active CORM-3, and GYY4137, whereas three groups underwent no ACS to serve as a sham. Sinusoidal perfusion, inflammatory response and cell death were quantified in exteriorized livers. Respiratory, liver, and renal dysfunction was assessed biochemically.

RESULTS

Hepatocellular death and the number of activated leukocytes within postsinusoidal venules were significantly increased in rats with ACS (16-fold increase, 17-fold leukocyte activation, respectively, P < 0.05). Administration of CORM-3 or GYY4137 resulted in a significant decrease of both parameters (P = 0.03 and P = 0.009). ACS resulted in an increase in markers of renal and liver injury; CORM-3 or GYY4137 partially restored levels to those seen in sham animals. Myeloperoxidase was significantly elevated in the ACS group in lung, liver, and small intestine (P = 0.0002, P = 0.01, and P = 0.08, respectively). CORM-3 treatment, but not GYY4137, was able to completely block the response (65 ± 11 U/ml and 92 ± 18 U/ml, respectively versus 110 ± 10U/ml in the ACS group, lung tissue).

CONCLUSIONS

We have demonstrated the effect of two molecules, CO and hydrogen sulphide, on tempering the reperfusion-associated metabolic and organ derangements in ACS. CORM-3 demonstrated a greater effect than GYY4137 and was able to restore most of the measured parameters to levels comparable to sham.

Lipopolysaccharide-induced neutrophil extracellular trap formation in canine neutrophils is dependent on histone H3 citrullination by peptidylarginine deiminase

Neutrophils release neutrophil extracellular traps (NETs), which are extracellular chromatin decorated with histones and antimicrobial proteins. Although known for antimicrobial properties, overzealous production of NETs (NETosis) may lead to cytotoxicity and multiple organ failure in sepsis. Pathogen-induced NETosis has been extensively studied in mice but its importance in dogs remains largely unknown. This study sought to characterize in vitro NETosis induced by E.coli LPS, including assessing the role of peptidylarginine deiminase (PAD) in canine NETosis. Neutrophils (1×10⁶ cells/ml) from healthy dogs were isolated and treated with 100μg/ml LPS, 100nM phorbol 12-myristate 13-acetate (PMA), or buffer for either 90 or 180min. NETs were assessed using fluorescence microscopy of living neutrophils and immunofluorescent microscopy. Supernatant and cellular debris were purified and cell-free DNA was quantified by spectrophotometry. The role of PAD was assessed by treating LPS- and PMA-activated neutrophils with 50, 100 or 200μM of the PAD inhibitor, Cl-amidine. In vitro NETosis was characterized by co-localization of cell-free DNA, citrullinated histone H3, and myeloperoxidase. LPS stimulation resulted in intracellular citrullination of histone H3. Compared to PMA chemically-induced NETosis, LPS resulted in smaller NETs with less extracellular citrullinated histone H3. Cl-amidine decreased citrullination of histones and NET production in either LPS- or PMA-stimulated neutrophils demonstrating that neutrophil PAD is essential for these cellular processes.

Interleukin-17A Aggravates Middle Ear Injury Induced by Streptococcus pneumoniae through the p38 Mitogen-Activated Protein Kinase Signaling Pathway

Acute otitis media (AOM) is one of the most common bacterial infectious diseases in children aged 2 to 7 years worldwide. We previously demonstrated that interleukin-17A (IL-17A) promotes an acute inflammatory response characterized by the influx of neutrophils into the middle ear cavity during Streptococcus pneumoniae-induced AOM. In general, the inflammatory response is viewed as an effector that frequently causes local tissue damage. However, little is known about the pathogenic effects of IL-17A in AOM. Here, we investigated the pathogenic effects of IL-17A by using wild-type (WT) and IL-17A knockout (KO) mouse models. The results showed that the pathogenic effects of AOM, including weight loss, histopathological changes, and proinflammatory cytokine production, were more severe in WT mice than in IL-17A KO mice, suggesting that IL-17A aggravates tissue damage in AOM. Furthermore, these pathogenic effects were found to be dependent on p38 mitogen-activated protein kinase (MAPK) and could be reversed in the presence of a p38 MAPK-specific inhibitor. It was also demonstrated that IL-17A promoted the production of neutrophil myeloperoxidase (MPO) through the p38 MAPK signaling pathway, which was responsible for the middle ear tissue injury. These data support the conclusion that IL-17A contributes to middle ear injury through the p38 MAPK signaling pathway.

Polysaccharides from Arnebia euchroma Ameliorated Endotoxic Fever and Acute Lung Injury in Rats Through Inhibiting Complement System

Arnebiaeuchroma (Royle) Johnst (Ruanzicao) is a traditional Chinese herbal medicine (TCM). It is extensively used in China and other countries for treatment of inflammatory diseases. It is known that hyper-activated complement system involves in the fever and acute lung injury (ALI) in rats. In our preliminary studies, anti-complementary activity of crude Arnebiaeuchroma polysaccharides (CAEP) had been demonstrated in vitro. This study aimed to investigate the role and mechanism of crude Arnebiaeuchroma polysaccharides (CAEP) using two animal models, which relate with inappropriate activation of complement system. In lipopolysaccharide (LPS)-induced fever model, the body temperature and leukocytes of peripheral blood in rats were significantly increased, while the complement levels of serum were remarkably decreased. CAEP administration alleviated the LPS-induced fever, reduced the number of leukocytes, and improved the levels of complement. Histological assay showed that there were severe damages and complement depositions in lung of the ALI rats. Further detection displayed that the oxidant stress was enhanced, and total hemolytic activity and C3/C4 levels in serum were decreased significantly in the ALI model group. Remarkably, CAEP not only attenuated the morphological injury, edema, and permeability in the lung but also significantly weakened the oxidant stress in bronchoalveolar lavage fluid (BALF) in the ALI rats. The levels of complement and complement depositions were improved by the CAEP treatment. In conclusion, the CAEP treatment ameliorated febrile response induced by LPS and acute lung injury induced by LPS plus ischemia-reperfusion. CAEP exerted beneficial effects on inflammatory disease potentially via inhibiting the inappropriate activation of complement system.

Histones and Neutrophil Extracellular Traps Enhance Tubular Necrosis and Remote Organ Injury in Ischemic AKI

Severe AKI is often associated with multiorgan dysfunction, but the mechanisms of this remote tissue injury are unknown. We hypothesized that renal necroinflammation releases cytotoxic molecules that may cause remote organ damage. In hypoxia-induced tubular epithelial cell necrosis in vitro, histone secretion from ischemic tubular cells primed neutrophils to form neutrophil extracellular traps. These traps induced tubular epithelial cell death and stimulated neutrophil extracellular trap formation in fresh neutrophils. In vivo, ischemia-reperfusion injury in the mouse kidney induced tubular necrosis, which preceded the expansion of localized and circulating neutrophil extracellular traps and the increased expression of inflammatory and injury-related genes. Pretreatment with inhibitors of neutrophil extracellular trap formation reduced kidney injury. Dual inhibition of neutrophil trap formation and tubular cell necrosis had an additive protective effect. Moreover, pretreatment with antihistone IgG suppressed ischemia-induced neutrophil extracellular trap formation and renal injury. Renal ischemic injury also increased the levels of circulating histones, and we detected neutrophil infiltration and TUNEL-positive cells in the lungs, liver, brain, and heart along with neutrophil extracellular trap accumulation in the lungs. Inhibition of neutrophil extracellular trap formation or of circulating histones reduced these effects as well. These data suggest that tubular necrosis and neutrophil extracellular trap formation accelerate kidney damage and remote organ dysfunction through cytokine and histone release and identify novel molecular targets to limit renal necroinflammation and multiorgan failure.

The critical role of myeloperoxidase in Streptococcus pneumoniae clearance and tissue damage during mouse acute otitis media

We have recently reported that neutrophils play a pivotal role in innate defense against Streptococcus pneumoniae ( Spn) during mouse acute otitis media (AOM). However, the underlying mechanism remains unclear. By constructing models of pneumococcal AOM in C57BL/6 mice and using a specific inhibitor in vivo, we investigated the role of myeloperoxidase (MPO), one of the most important protein components of neutrophils. Experiment results showed a significant increase in MPO production of the recruited neutrophils in Spn-infected mice. Neutrophils killed Spn in a MPO-dependent manner. MPO facilitated the generation of reactive oxygen species (ROS), and consequently promoted Spn clearance at an early stage and exacerbated tissue damage. Moreover, MPO induced neutrophil apoptosis and necrosis, which, in turn, worsened tissue damage. In summary, our study demonstrates that neutrophil MPO plays a paradoxical role in bacterial clearance and tissue damage in pneumococcal AOM.

The Matrine Derivate MASM Prolongs Survival, Attenuates Inflammation, and Reduces Organ Injury in Murine Established Lethal Sepsis

BACKGROUND

 MASM, a novel derivative of matrine, has inhibitory effects on activation of macrophages, dendritic cells, and hepatic stellate cells and binds to ribosomal protein S5 (RPS5). This study was designed to evaluate the effect of MASM on murine-established lethal sepsis and its mechanisms.

METHODS

 Mouse peritoneal macrophages and RAW264.7 cells that were infected with recombinant lentiviruses encoding shRPS5 were incubated with lipopolysaccharide (LPS) in the absence or presence of MASM in vitro. Endotoxemia induced by LPS injection and sepsis induced by cecal ligation and puncture was followed by MASM treatment.

RESULTS

 MASM markedly attenuated LPS-induced release and messenger RNA expression of tumor necrosis factor α, interleukin 6, and NO/inducible NO synthase in murine peritoneal macrophages and RAW264.7 cells. Meanwhile, MASM inhibited LPS-induced activation of nuclear factor κB and MAPK pathways. Consistently, RPS5 suppressed LPS-induced inflammatory responses and at least in part mediated the antiinflammatory effect of MASM in vitro. Remarkably, delayed administration of MASM could significantly reduce mortality in mouse sepsis models, which was associated with the reduction in the inflammatory response, the attenuation in multiple organ injury, and the enhanced bacterial clearance.

CONCLUSIONS

 MASM could be further explored for the treatments of sepsis, especially for administration later after the onset of sepsis.

WNT Agonist Decreases Tissue Damage and Improves Renal Function After Ischemia-Reperfusion

Renal ischemia-reperfusion (IR) injury (IRI) after shock states or transplantation causes tissue damage and delayed graft function, respectively. The Wnt/β-catenin signaling pathway plays a critical role in nephrogenesis. We therefore hypothesized that pharmacological activation of the Wnt/β-catenin signaling by the Wnt agonist, a synthetic pyrimidine, could protect kidneys from IRI. Adult male rats were subjected to bilateral clamping of the renal pedicles with microvascular clips for 60 min, followed by reperfusion. The Wnt agonist (5 mg/kg body weight) or vehicle (20% dimethyl sulfoxide in saline) was administered intravenously 1 h before ischemia. Blood and renal tissues were collected 24 h after IR for evaluation. Renal IR caused a significant reduction of β-catenin and its downstream target gene cyclin D1 by 65% and 39%, respectively, compared with the sham, whereas the Wnt agonist restored them to sham levels. The number and intensity of cells staining with the proliferation marker Ki67 in ischematized kidneys were enhanced by the Wnt agonist. The integrity of the renal histological architecture in the Wnt agonist group was better preserved than the vehicle group. The Wnt agonist significantly lowered serum levels of creatinine, aspartate aminotransferase, and lactate dehydrogenase and inhibited the production of interleukin 6 and interleukin 1β and myeloperoxidase activities. Lastly, the Wnt agonist reduced inducible nitric oxide synthase, nitrotyrosine proteins, and 4-hydroxynonenal in the kidneys by 60%, 47%, and 21%, respectively, compared with the vehicle. These results indicate that the Wnt agonist improves renal regeneration and function while attenuating inflammation and oxidative stress in the kidneys after IR. Thus, pharmacologic stimulation of the Wnt/β-catenin signaling provides a beneficial effect on the prevention of renal IRI.

Life and death at the mucosal-luminal interface: New perspectives on human intestinal ischemia-reperfusion

Intestinal ischemia is a frequently observed phenomenon. Morbidity and mortality rates are extraordinarily high and did not improve over the past decades. This is in part attributable to limited knowledge on the pathophysiology of intestinal ischemia-reperfusion (IR) in man, the paucity in preventive and/or therapeutic options and the lack of early diagnostic markers for intestinal ischemia. To improve our knowledge and solve clinically important questions regarding intestinal IR, we developed a human experimental intestinal IR model. With this model, we were able to gain insight into the mechanisms that allow the human gut to withstand short periods of IR without the development of severe inflammatory responses. The purpose of this review is to overview the most relevant recent advances in our understanding of the pathophysiology of human intestinal IR, as well as the (potential) future clinical implications.

Neutrophil-Mediated Regulation of Innate and Adaptive Immunity: The Role of Myeloperoxidase

Neutrophils are no longer seen as leukocytes with a sole function of being the essential first responders in the removal of pathogens at sites of infection. Being armed with numerous pro- and anti-inflammatory mediators, these phagocytes can also contribute to the development of various autoimmune diseases and can positively or negatively regulate the generation of adaptive immune responses. In this review, we will discuss how myeloperoxidase, the most abundant neutrophil granule protein, plays a key role in the various functions of neutrophils in innate and adaptive immunity.

Evaluation of the effects of ischemic preconditioning on the hematological parameters of rats subjected to intestinal ischemia and reperfusion

OBJECTIVES

Intestinal ischemia/reperfusion often leads to acute lung injury and multiple organ failure. Ischemic preconditioning is protective in nature and reduces tissue injuries in animal and human models. Although hematimetric parameters are widely used as diagnostic tools, there is no report of the influence of intestinal ischemia/reperfusion and ischemic preconditioning on such parameters. We evaluated the hematological changes during ischemia/reperfusion and preconditioning in rats.

METHODS

Forty healthy rats were divided into four groups: control, laparotomy, intestinal ischemia/reperfusion and ischemic preconditioning. The intestinal ischemia/reperfusion group received 45 min of superior mesenteric artery occlusion, while the ischemic preconditioning group received 10 min of short ischemia and reperfusion before 45 min of prolonged occlusion. A cell counter was used to analyze blood obtained from rats before and after the surgical procedures and the hematological results were compared among the groups.

RESULTS

The results showed significant differences in hematimetric parameters among the groups. The parameters that showed significant differences included lymphocyte, white blood cells and granulocyte counts; hematocrit; mean corpuscular hemoglobin concentration; red cell deviation width; platelet count; mean platelet volume; plateletcrit and platelet distribution width.

CONCLUSION

The most remarkable parameters were those related to leukocytes and platelets. Some of the data, including the lymphocyte and granulocytes counts, suggest that ischemic preconditioning attenuates the effect of intestinal ischemia/reperfusion on circulating blood cells. Our work contributes to a better understanding of the hematological responses after intestinal ischemia/reperfusion and IPC, and the present findings may also be used as predictive values.

Catheter-based induction of renal ischemia/reperfusion in swine: description of an experimental model

Several techniques to induce renal ischemia have been proposed: clamp, PVA particles, and catheter-balloon. We report the development of a controlled, single-insult model of unilateral renal ischemia/reperfusion (I/R) without contralateral nephrectomy, using a suitable model, the pig. This is a balloon-catheter-based model using a percutaneous, interventional radiology procedure. One angioplasty balloon-catheter was placed into the right renal artery and inflated for 120 min and reperfusion over 24 h. Serial serums were sampled from the inferior vena cava and urine was directly sampled from the bladder throughout the experiment, and both kidneys were excised after 24 h of reperfusion. Analyses of renal structure and function were performed by hematoxylin-eosin/periodic Acid-Schiff, serum creatinine (SCr), blood urea nitrogen (BUN), fractional excretion of ions, and glucose, SDS-PAGE analysis of urinary proteins, and serum neutrophil gelatinase-associated lipocalin (NGAL). Total nitrated protein was quantified to characterize oxidative stress. Acute tubular necrosis (ATN) was identified in every animal, but only two animals showed levels of SCr above 150% of baseline values. As expected, I/R increased SCr and BUN. Fractional sodium, potassium, chloride, and bicarbonate excretion were modulated during ischemia. Serum-nitrated proteins and NGAL had two profiles: decreased with ischemia and increased after reperfusion. This decline was associated with increased protein excretion during ischemia and early reperfusion. Altogether, these data show that the renal I/R model can be performed by percutaneous approach in the swine model. This is a suitable translational model to study new early renal ischemic biomarkers and pathophysiological mechanisms in renal ischemia.